During the life cycle of a wellbore, many tools may be used within the wellbore. In some cases, it may be desirable to selectively activate or change configuration or operating mode of a downhole tool while ensuring that the tools are turned on and off or are reconfigured only when desired. Typically, such operations may be carried out by using a single drop ball, multiple drop balls, an electro-mechanical actuator initiated by a surface downlink, or by a hydraulic pressure differential generated by fluid flow. Other downhole tools may be activated or reconfigured by constantly-cycling indexing mechanisms.